PURPOSE: To assess the MR findings of Tolosa-Hunt syndrome and to evaluat differential point of cavernous sinus lesions. MATERIALS AND METHODS: Eleven cases of Tolosa-Hunt syndrome were evaluated by MRI with specific regard to the shape of cavernous sinus, signal intensity, and pattern of enhancement. Other associated findings were also anlaysed. RESULTS: Two patients had normal MR features of the cavernous sinus. When compared with the contralateral normal cavernous sinus, the involved cavernous sinus was enlarged in six of the nine patients. The outer dural margin was convex and bulged laterally in 6 cases, flat in 2 cases, and concave in 1 case. Of the nine patients, five had iso-signal intensity and four had low signal intensity relative to gray matter on short TR/short TE. Three had isosignal intensity and 6 were not detectale on long TR/short and long TE pulse sequence. Contrast enhancement was seen in 8 cases ;7 cases showed homogeneous enhancement, 1 case heterogeneous enhancement. CONCLUSION: In the appropriate clinical setting of painful ophthalmoplegia, MR findings of cavernous sinus abnormality that consist of iso to low signal intensity on short TR/short TE images and isointense or undetectale mass on long TR/short TE or long TR/Iong TE images may suggest the dignosis of Tolosa-Hunt syndrome.